1. Field of the Invention
This invention relates generally to the art of loose-leaf ring binders and particularly to paper lifters co-acting with binder rings to manage papers.
2. Prior Art
A paper lifter is a generally rectangular plate having apertures adapted to fit onto the rings in a loose leaf ring binder. As a member of a type two lever system the lifter also interacts with the binder book covers and a protective plate for the ring mechanism. The elongated side of the rectangle is generally aligned with the back of the ring binder. The apertures are placed approximately in the middle of the transverse side of the rectangle. Extending outward over the binder cover is a generally flat surface adapted to lie against the cover and to act as an effort (input) arm of the lever system. Extending inwards toward the center of the ring mechanisms is a surface adapted to abut and slide against the ring mechanism and to provide a load arm and fulcrum for a type two lever system. Load points, for lifting papers, are generally at or near the shoulders of the apertures. The prior an generally refers to ring binders, loose-leaf ring binders, rings or split rings, paper lifters, sheet lifters, paper inserts, punched papers, pre-punched sheet, and the like. It is understood that paper sheets and rings coact, thus the spacing of punched holes and rings are a combination. Although "rings" in general are circular, or semi circular in shape, they are in effect merely prongs which receive the punched papers or sheets, and may have many shapes. These range from true rings, to straight bars or rods, to substantially rectangular prongs, and to paired combinations of rings and bars or other paired combination of shapes. The following uses of "rings" will not be restricted to circular shapes, but will include any shapes and labels in general use.
Three rings, or sets of split rings, are the most common number of rings in a given loose-leaf binder. This constitute a set which is generally duplicated in the number of holes in the paper inserts, punched papers, sheet, and paper lifters. However, two and seven rings are common examples in combination with corresponding sets of punched holes in loose sheet.
Prior art portrays several sheet lifters. These lifters have in common a general lack of acceptance by the public; reasons include nonperformance, too unwieldy to use, and too expensive to produce. General reviews of the prior art are found in the references below and will therefore not be repeated. Specific attention will be directed to the following patents:
1. Lewis R. Beyer: "Sheet Lifter," U.S. Pat. No. 3,366,118, dated Jan. 30, 1968, hereinafter Beyer; PA1 2. R. J. Kenkott: "Sheet Lifting Device for a Loose Leaf Binder," U.S. Pat. No. 2,276,987, dated Mar. 17, 1942, hereinafter Kenkott; and PA1 3. J. B. Stuerke: "Fulcrum for Loose Leaf Binders," U.S. Pat. No. 2,505,694, dated Apr. 25, 1950, hereinafter Stuercke.
The Beyer patent shows a standard ring binder with a protective plate over the ring mechanism. An elongated paper lifter inserts transversely over the rings through a plurality of apertures. An inner curved surface extends over the plate and ends in an uninterrupted edge; the curvature is sufficient to rotate the edge to lie flat against the inner circumference of each ring. The apertures and the edge are pressure points acting against the rings; they span an angular arc that is large enough to create components of force that move the lifter along the rings. Outward-sloping ribs are placed on top of the lifter and extend over and well beyond the apertures; their purpose is to slide binder papers away from the rings to prevent tearing of the papers. Ribs are also placed on the underside of the curved surface to prevent opposite pairs of lifters to interlock.
The Beyer patent places emphasis on obtaining sufficient spacing between the pressure points to move the lifter along the rings. The separation between the inner edge and the apertures is therefore determined while both pressure point are against the rings. As a consequence, when the lifter lies flat (ring binder open), the inner edge does not contact the protected plate but is instead suspended well above the plate. Only after rotating a considerable angle following first motion does the inner edge reach the plate. During this initial motion the lifter pivots about the apertures only; consequently, there is no motion of the lifter apertures along the rings. The apertures therefore catch and tear the papers in the binder. The outward-sloping ribs are inserted to solve this problem, thus causing additional complexity.
The Kencott patent also shows a standard ring binder with a protective plate and lifter apertures engaged with the rings. The load end cuffs upward over the plate and then closes upon itself to form a closed rocker with an upper shelf. The end of the shelf has a small semicircular notch that abuts the ring. In operation the lifter leverages on the curved rocker portion and rides up the ring on the notch in the shelf end; the shelf pushes the paper sheets.
It is noted that the rockers must be large to provide a high enough step to raise the paper sheets sufficiently. Thus the rockers become large enough to abut each other when installed as opposing pairs in the ring binder, yet they may not be large enough to fully raise the paper sheets. However, the suspected deficiency is neatly avoided by claiming beneficial co-action between the opposing lifters. One suspects, however, that this co-action may result in un-beneficial entanglements.
The Stuercke patent shows improvements upon the Kencott invention. One improvement consists of a raised surface mounted on top of the protected plate. This surface serves as an artificial protective plate and raises the height of the lifter. A second improvement is a guide that engages the closed rocker and limits unwanted movements of the lifter. These improvements expressly confirm the reservations noted above about the Kencott invention; yet they solves the problem. The result, however, is a cumbersome addition to a prior device.